Mcswain dam
Mcswain
Mcswain, a hydroelectric dam located in Mariposa, California, is a public utility owned and regulated by the state of California. Completed in 1966, this rockfill dam stands at a height of 97 feet and has a maximum storage capacity of 9730 acre-feet. With its primary purpose being hydroelectric power generation, Mcswain also serves irrigation and recreation purposes, making it a versatile water resource in the region.
Managed by the Federal Energy Regulatory Commission, Mcswain boasts a spillway width of 625 feet and a maximum discharge capacity of 250,000 cubic feet per second. Its hazard potential is classified as high, with a moderate risk assessment score of 3. Despite its condition assessment being labeled as not available, the dam is regularly inspected, with the last inspection conducted in September 2020. The emergency action plan for Mcswain was last revised in January 2021, ensuring that necessary measures are in place to mitigate any potential risks associated with the dam.
In the picturesque setting along the Merced River, Mcswain not only provides essential water resources but also contributes to the local economy and recreational activities. With its strategic location and robust infrastructure, this dam continues to play a vital role in water management and power generation in the region, while adhering to strict regulatory standards set by state and federal agencies.
Plan around the weather
Same NOAA / yr.no feed Snoflo's iOS app uses. Watch the precipitation column on the meteogram -- rain on the basin upstream typically lifts inflow 24-72 hours later.
Next 5 days, hour by hour
Temperature line with weather symbols on top, snow + rain accumulation as columns, humidity as a dotted line.
5-day forecast table
Every 3 hours, broken out across temperature, snow, rain, humidity, and wind. Each cell is colour-coded relative to the column min/max.
| Time | Condition | Temp (°F) | Snow (in) | Rain (in) | Humidity (%) | Wind (mps) | Wind dir |
|---|---|---|---|---|---|---|---|
| Loading detailed forecast… | |||||||
15-day temperature & precipitation
Daily temperatures, snow, and rain projected over the next two weeks.
Nearby streamflow gauges
USGS streamgauges around Mcswain -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Turlock Cn Nr La Grange Ca | 1,840 cfs | → |
| Tuolumne R Bl Lagrange Dam Nr Lagrange Ca | 159 cfs | → |
| Modesto Cn Nr La Grange Ca | 1,210 cfs | → |
| Big C Ab Whites Gulch Nr Groveland Ca | 0 cfs | → |
| Tuolumne R Bl Early Intake Nr Mather Ca | 143 cfs | → |
| Cherry C Bl Dion R Holm Ph | 84 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Mcswain.
Boat launches
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Campgrounds
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Fishing spots
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River runs
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About Mcswain
Where does the data for Mcswain come from?
Structural and regulatory data come from the U.S. Army Corps of Engineers' National Inventory of Dams (NID). Weather forecast comes from NOAA / yr.no -- the same feed Snoflo's iOS app uses.
How often is the report updated?
NID structural data refreshes annually as the Corps publishes updated assessments. The weather forecast refreshes throughout the day.
What does the High hazard rating mean?
The Corps of Engineers' hazard potential classification grades probable consequences if the dam fails: High = probable loss of human life; Significant = no probable loss of human life but possible economic loss / environmental damage; Low = no probable loss of human life, only minor economic / environmental losses. See the Dam Data Reference card below for the full definitions.
What's "% of normal"?
The current storage value compared to the historical average storage on this calendar day. 100% = right on average; values above 100% mean above-normal storage (wet year); values below mean below-normal (dry year or drought).
Can I get alerts when storage crosses a threshold?
Yes -- alerts are managed in the Snoflo iOS app. Favorite this dam, set a threshold, and you'll get a push the moment conditions cross.
Dam data reference
Condition Assessment
- Satisfactory
- No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
- Fair
- No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action.
- Poor
- A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency.
- Unsatisfactory
- A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
- Not Rated
- The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Hazard Potential Classification
- High
- Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
- Significant
- Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environmental damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
- Low
- Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
- Undetermined
- Dams for which a downstream hazard potential has not been designated or is not provided.